This project is an attempt to elucidate the biochemical mechanisms responsible for morphological differentiation in the fungus, Mucor rouxii. Our study is focused on the cell wall. We would like to learn how the fungus elaborates the different types of cell walls that characterize each step of its life cycle; what enzymes are involved in wall formation; how these polymers are synthesized and assembled into cell walls with various characteristic shapes; what biochemical controls regulate the formation and spatial deposition of wall constituents; what cytoplasmic structures participate in the process of wall formation. We are using the process of chitin biosynthesis as a model system for these studies. We have developed a procedure to synthesize chitin microfibrils in vitro. The enzyme that makes these fibrils, chitin synthetase, is in the form of minute characteristic vesicle-like structures, the size of a virus. We call these particles chitosomes. Our immediate goals are to characterize the chitosome and provide unequivocal proof of their existence in the living cell, to trace their ontogeny from their point of formation to their point of operation.